The desirability of guarding medical needles to reduce needle-stick injury is well recognised, as is the desirability of reducing blood-splash from needles immediately after use. `Blood-splash` is used herein generically to signify the dripping of any liquid from the point of a used needle and is a particular danger with needle assemblies because their trailing tubes often contain blood. There are other important desiderata of a more practical nature relating to needle guards: the guard should not interfere with the positioning and control of the needle during use; since many medical needles are manufactured without guards, the guard should be easy and safe to fit to a pre-existing needle assembly; on the other hand, it should be suitable for fitting to needle assemblies at the time of manufacture; and, since most needles will be used only once, the guard also needs to be inexpensive and disposable. The most pertinent prior art known to the applicant which addresses such desiderata is referenced below.
The guards of relevance to this invention are of two general classes: (i) those which fit around and slide along the trailing tube and over the needle from its rear end, and (ii) those which permanently house the needle in such a way that it can be extended from the guard for use or withdrawn into the guard for protection. Guards of the first class have the advantage that they can be moved well clear of the needle along the trailing tube so that the needle can be inserted without interference from the guard. Furthermore, guards of the first class can be easily attached around the trailing tube of a standard needle by the user, whereas those of the second are generally applied to the needle during manufacture and require the use of non-standard needle assemblies.
Guards of the first class may be divided into three types. First, there are those in which the front ends are split longitudinally into fingers that flex outwards when the guard is pushed onto the hub. The fingers typically ride along the needle wings and then snap together around the wings to retain the needle in a guarded position. Examples are disclosed in the applicant's US patent No. 5,827,239 which can be assembled by the user around the trailing tube of a standard winged needle assembly or fitted over the tube at the time of manufacture to form a combined needle and guard assembly. Others are disclosed in U.S. Pat. No. 5,069,341 to Barbieri et al, U.S. Pat. No. 5,192,275 to Burns, U.S. Pat. No. 5,330,438 to Gollobin, U.S. Pat. No. 5,279,588 to Nicoletti, U.S. Pat. No. 5,350,368 to Shields and U.S. Pat. Nos. 5,562,636 and 5,562,637 to Utterberg. Guards of this type are not ideal because blood splash can occur through their open front ends and/or side slots.
The prior art of the first type which is of most interest from the standpoint of the present invention is the embodiment illustrated in FIGS. 24 to 26 of the Nicoletti patent identified above, in which the front end of a tubular guard comprises two opposing fingers hingedly attached to the rear portion of the guard. Each finger has a hole therethrough to take one wing of the needle. To fit such a guard over a needle, the needle must be withdrawn from the patient and the fingers manipulated to fit the wings into the holes. Then the fingers must be pushed together to enclose the needle. Not only is there danger of needle stick blood-splash from the exposed used needle during this manoeuvre, but the user is likely to touch the sides of the exposed needle as he/she attempts to insert the wings into their slots in the fingers of the guard.
The second type of tube-mounted guard is also intend for use with winged needle assemblies but it has a single wide open-ended slot so that the needle can be withdrawn into the guard by folding its wings together and entering both wings into the slot. Examples of this type of guard are disclosed in U.S. Pat. No. 4,941,881 to Masters et al and in U.S. Pat. No. 5,498,241 to Fabrozzi. Not only can blood-splash occur through the open front ends of these guards, but the wide slot provides another route for blood-splash and may also allow the guard and needle to be misaligned so that the point of a guarded needle can extend through the slot.
The third type of guard of the first class is that suited for use with wingless needles. A guard of this type take the form of a tapered sleeve into which the hub of a used needle can be pulled by its tube and jammed in the rear end thereof(eg, U.S. Pat. No. 5,401,250 to Shields). However, blood-splash can still occur from the open front end of the sleeve and frictional jamming is an insecure manner of securing the needle and its hub in a guard.
The second class of guard (where the needle is permanently mounted in the guard) is well represented in the art; for example, U.S. Pat. No. 4,676,783 to Jagger et al, U.S. Pat. No. 5,088,982 to Ryan, U.S. Pat. Nos. 5,112,311, 5,290,264 & 5,433,703 to Utterberg, and U.S. Pat. No. 5,120,320 to Fayngold. Not only do such guards generally have open front ends through which blood-splash can occur, but the slots formed to slidingly accommodate the needle wings provide additional apertures through which blood-splash may occur and can allow the point of the needle itself to protrude. In one case (Utterberg U.S. Pat. No. 5,112,311 FIGS. 23-25), the slots are fitted with `curtains` or flaps (identified by numeral 403 by Utterberg) to mitigate this danger but, if the curtains are to be effective in that regard, they will make it difficult to move the wings of the needle assembly along the slots. In another case (U.S. Pat. No. 5,433,703 to Utterberg), a separate cap is provided for covering the open end of the guard after the needle has been withdrawn therein, but the cap is another item to manipulate and is an additional expense. Not all guards of the second class are for use with winged needles. For example, U.S. Pat. No. 5,382,240 to Lam and European patent 722,749 to BOC Group disclose needle guards within which wingless needle assemblies are slidingly mounted. The first of these has an open front end while, in the second, the needle hub is provided with stubby wing-like protrusions that ride in side slots formed a tubular housing. Though both such end and side openings provide the opportunity for blood-splash contamination, the BOC patent is of particular interest because it discloses the use of a sliding or hinged gate on the front end of the guard that can be manually operated to close that end after the needle has been withdrawn into the guard tube. Again, however, the addition of such gates is expensive and possibly unreliable since they require additional and separate moving parts.